It happened on Saturday 26 May at a busy road junction where three roads meet near the entrance to Les Genats estate.
A car and motorbike are believed to have collided at around 16:00 with the road blocked for some time afterwards.
Guernsey police, ambulance and fire and rescue services were all called to deal with the incident. Members of the public assisted by keeping the flow of traffic away from the scene of the accident while the male victim was treated at the site before being taken to the emergency department at the Princess Elizabeth Hospital for further treatment.
The road was reopened by 18:00 but signs remained advising motoroists of oil left on the road.
